The field of the invention relates to cleaning apparatus for cleaning carriers used to hold and process semiconductor wafers, substrates, flat panel displays and similar flat articles requiring low contamination levels.
The processing of semiconductor wafers, substrates, photomasks, flat panel displays, data disks, optical media and other articles relating to the semiconductor industry (collectively referred to here as xe2x80x9cwafersxe2x80x9d) is very sensitive to problems of contamination. These articles require extremely low contamination levels. Even microscopic contaminants can cause defects. Accordingly, it is necessary to maintain a high level of cleanliness during virtually all stages of manufacture.
Semiconductor wafers are typically processed in batches. Batch handling may occur throughout the entire production process, or for one or more processing steps or related handling operations. Batch processing almost always uses some type of carrier to hold the wafers. The wafer carriers can be of various designs. Carriers in the form of a protective case or box are often used. In these types of carriers, the wafers are held and enclosed against contamination during travel within the processing facility. The wafer carriers must be cleaned, to avoid having particles and contaminants on the carriers contaminate the wafers. However, cleaning carriers or boxes can he difficult due to their size and shape, and because they may have features such as slots, grooves or apertures.
Box carriers have been successfully cleaned in centrifugal cleaners. See, for example, U.S. Pat. No. 5,738,128, incorporated herein by reference. In these centrifugal cleaners, the box is loaded onto a rotor, with the open top or front side of the box facing radially outwardly from the rotor. The box is sprayed with cleaning fluids, and then with drying gases, while the rotor turns. Centrifugal force helps to remove cleaning fluids from the box and to help dry it.
Ease of loading and unloading boxes, and their doors into and out of the rotor, and maintaining the rotor in balance under various conditions, remain as engineering challenges.
In a first aspect of the invention, a system for cleaning carriers used for handling wafers includes a box cleaner having a rotor within an enclosure. Box holder assemblies on the rotor include upper and lower hooks for securing boxes to the rotor. A box door holder assembly is also provided on the rotor. The box door holder assembly preferably has a plurality of box door holding positions. Each box door holding position advantageously has a door guide and door hooks for holding a door. The box door holder assembly allows both the boxes and their doors to be cleaned with the centrifugal cleaner, avoiding the need for separate cleaning of the doors.
In a second and separate aspect, the rotor is provided with an even number of box holder assemblies symmetrically spaced about the rotor and an even number of door holder assemblies symmetrically spaced about the rotor. This helps to allow the rotor to avoid out of balance conditions
Other and further objects, inventive features, and advantages, will appear hereinafter. The invention resides as well in subcombinations of the features described.